Fig. 3.
The statistics of monthly average concentrations of a NH3, b NO2, and c HNO3 during the sampling periods at the five sites. The arrows denote N fertilizer application for the maize-wheat crop rotation system at SZ, QZ, and YC
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.